Hey guys, whats going on.
I'm looking for any help or ideas, I currently drive a 5.7L Vortec, 1999 Tahoe. I love my truck, even after all these years. This is the first time its ever given me any real issue that i've had trouble fixing. Usually it's something simple or straight forward.
As of right now I have no heat in my truck, I've done everything i could possibly think of and im praying someone has some insight on this, before you start rattling your brains with what could be wrong. Let me tell you what i've done (Actually, i've done twice to make sure i had it right the first time lol..)...

So far i've replaced the ---
- Blend door actuator (Passenger side)
- Thermostat *195 degree* (I checked with boiling water and a temp gun to make sure it opens at the proper temperature)
- Heater control valve and lines to and from heater core (No leaks, the control valve works properly and i have flow through the heater core)
- Heater core (It currently only gets hot when im in park and i rev the engine to around 2500-3000 RPMS, otherwise it remains luke warm)
- I have the right amount of coolant, and yes, I've burped the system.
- I've also checked all my lines for clogs and leaks...Nothing.

And one last thing, when i do rev up the engine to 2500-3000RPMS and the heater core does get hot. As soon as i put on the blower, within only a few seconds its back to luke warm again. I occasionally feel a draft comming in the truck from outside, does anyone know the location of the fresh air door that brings the outside air into the cabin so i check to see if it is stuck open?




Please guys! i need help, thankyou in advance